Nowadays, some thermoelectric plants use heavy fuel oil as fuel, which is produced diluting the vacuum residue with lighter refining oil products as diesel, kerosene and other cyclic oils to reduce its viscosity and facilitate its transportation. The use of such diluents make expensive the resulting fuel.
Moreover, the petroleum production in Mexico tends to increase in heavy crude oil extraction compared to light crude oil, leading to petroleum industry to process heavier crude oils, and improve at the same time, the efficiency of the refining processes; consequently, the oil refining residues produced shows higher values than before of viscosity, sulphur, sodium and vanadium; causing that the heavy fuel oil used by industry in general, and by thermoelectric plants in particular, to be more viscous and difficult to burn.
One way to reduce the viscosity of heavy hydrocarbons is emulsify them in water, the resulting fuel is easier than the original one to be transported for burning in the combustion equipment. The preparation of emulsions involves the dispersion of droplets of one liquid in another immiscible liquid. In the case of the vacuum residue, which is a complex heterogeneous system due to the amount and structure of its compounds and that is a hydrophobic material, can be dispersed in water—the aqueous medium or continuous phase- to form an emulsion of oil in water type; that avoids the addition of diluents which are higher-value products.
Ideas have been raised up and emulsified fuels has been developed from natural materials, such as bituminous material from the Orinoco riverbank, which was used to produce the so-called “Orimulsion”. These fuels does not come from industrially processed materials; thus, the ingredients, proportions, temperature and operating conditions differ substantially from those of this invention.
However, there is another emulsified fuel obtained from processed materials, whose patent (MX/PA/01003592), relates to continuous and batch processes to prepare it from vacuum residue of the oil refining. The procedure is limited in both continuous and batch processes, because it requires the use of a chemical substance as a stabilizer additionally of a surfactant to prepare the emulsion, and claims a vacuum residue and distilled water with specific characteristics. In that patent, the weight proportions for each component of emulsified fuel are as follows: 69 to 75% by weight of refining residues; 23.9 to 29.9% by weight of water; 0.5 to 1.5% by weight of surfactant and 0.05 to 0.15% by weight of stabilizer.
There also exists another patent (MX/A/06002412) in which the authors have improved the procedure contained in the MX/PA/01003592 patent referred above. Now, this patent, MX/A/06002412, comprises a continuous and in batch procedures for the preparation of emulsified fuels coming from processed materials of the vacuum unit of the oil refining; this procedure is limited in both continuous and batch processes, because it requires the use of a diluent during the preparation of the emulsion, and also claims a vacuum residue and water with specific characteristics. In that patent, the weight proportions for each component of emulsified fuel are as follows: 65 to 71% by weight of refining residues, 2 to 3% by weight of diluent respect to the residue, 27 to 33% by weight of water and 1 to 3% by weight of surfactant. It should also be noted that in this patent, no substance to stabilize the emulsion is used, but a diluent is required and the surfactant values used are higher than that in the MX/PA/01003592 patent referred initially.
In conclusion, it is important to establish that the main object of our invention is to provide to both oil and industrial sectors of a process for preparing a fuel-in-water emulsion in both continuous or in batch process. Process characterized because it does not require the use of chemical substances as stabilizers or diluents for its preparation, the vacuum residue is not limited to specific characteristics, and the water used can be of three types: distilled, tap water or salt water (seawater), and requires low concentration of a nonionic surfactant from 0.1 to 1% by weight. The emulsions obtained have proportions from 70 to 90% by weight of refining residues, 10 to 30% by weight of water and from 0.1 to 1% by weight of surfactant.
A further object of our invention is the emulsified fuel in water, produced from residues of oil refining processes, such as residues of atmospheric and vacuum distillation, heavy fuel oils and similar, and this fuel can be used in industrial combustion equipment such as boilers, fired heaters, process furnaces and similar equipment. This fuel is efficient to its burned; because the fuel oil droplets have the best size to be completely burned into the flame, which has a favorable effect to reduce the unburned particle emissions In addition, the emulsified fuel remains stable for an enough period for its storage and subsequent injection to the combustion equipment.
These and other objects of the present invention are described in more detail in the following chapters.
The best-known method to prepare emulsified fuels in water from petroleum residuals, object of the present invention, is presented in the section of detailed description of the invention.